Download Pig Dissection - Mo`Hearn Biology

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Fetal Pig Dissection: External Anatomy PART I
External Anatomy—you need a pan, pig, and ruler
1.
LABEL the pig to the right
Medial: toward the midline or middle of the body
Lateral: toward the outside of the body
Proximal: close to a point of reference
Distal: farther from a point of reference
2. Determine the sex of your pig by looking for the urogenital
opening.
On females, this opening is located near the anus. On males, the
opening is located near the umbilical cord. If your pig is female, you
should also note that urogenital papilla is present near the genital
opening. Males do not have urogenital papilla. Both males and
females have rows of nipples, and the umbilical cord will be present
in both.
What sex is your pig? _________
3. Open the pig’s mouth and locate the hard and soft palate on the roof of the mouth. Note the taste buds
(also known as sensory papillae) on the side of the tongue. Locate the esophagus at the back of the mouth.
Feel the edge of the mouth for teeth.
Does the fetal pig have teeth? ________
________
Are humans born with teeth?
4. Gestation for the fetal pig is 112-115 days. The length of the fetal pig can give you a rough estimate of its
age.
11mm – 21 days
17 mm – 35 days
2.8 cm – 49 days
How old is your fetal pig?
4 cm – 56 days
__________
22 cm – 100 days
30 cm -- birth
5. Observe the toes of the pig. How many toes are on the feet? ___________________
Do they have an odd or even number of toes? _________________
6. Observe the eyes of the pig, carefully remove the eyelid so that you can view the eye underneath. Does it
seem well developed?__________Do you think pigs are born with their eyes open or shut?
__________________
Checkpoint STAMP—this will get you tools and pins
The Anatomy of the Fetal Pig—PART II
Use a scratch paper to write the names of organs listed below. Be sure
to follow all directions and to get stamped every couple organs.
The Incision
Place your fetal pig in the dissecting pan ventral side up. Use string to "hog-tie" your pig
so that the legs are spread eagle and not in your way. Use scissors to cut through the
skin and muscles according to the diagram. Do not remove the umbilical cord. In the first
section, you will only examine the abdominal cavity (the area below the ribcage).
After completing the cuts, locate the umbilical vein that leads from the umbilical cord to
the liver. You will need to cut this vein in order to open up the abdominal cavity.
Your pig may be filled with water and preservative, drain over the sink if necessary and
rinse organs. Locate each of the organs below, check the box.
1. Diaphragm. This muscle divides the thoracic and abdominal cavity and is located near the ribcage. The diaphragm
aids in breathing.
2. Liver. This structure is lobed and is the largest organ in the body. The liver is responsible for making bile for digestion.
3. Gall bladder. This greenish organ is located underneath the liver; the bile duct attaches the gall bladder to the
duodenum. The gall bladder stores bile and sends it to the duodenum, via the bile duct.
4. Stomach. A pouch shaped organ that rests just underneath and to the pig's left. At the top of the stomach, you'll find
the esophagus. The stomach is responsible for churching and breaking down food.
5. At each end of the stomach are valves that regulate food entering and leaving the stomach. At the esophagus is the
cardiac sphincter valve, and at the duodenum is the pyloric sphincter valve. View the inside of the stomach by slicing
it open lengthwise.
Checkpoint STAMP
6. The stomach leads to the small intestine, which is composed of the duodenum (straight portion just after the
stomach) and the ileum (curly part).
7. The ileum is held together by mesentery. In the small intestine, further digestion occurs and nutrients are absorbed
through the arteries in the mesentery. These arteries are called mesenteric arteries.
8. Pancreas: a bumpy organ located along the underside of the stomach, a pancreatic duct leads to the duodenum.
The pancreas makes insulin, which is necessary for the proper uptake of sugars from the blood.
9. Spleen: a flattened organ that lies across the stomach and toward the extreme left side of the pig. The spleen stores
blood and is not part of the digestive system. On the underside of the spleen, locate the splenic artery.
10. At the end of the ileum, where it widens to become the large intestine, a "dead-end" branch is visible. This is the
cecum. The cecum helps the pig digest plant material.
11. The large intestine can be traced to the rectum. The rectum lies toward the back of the pig and will not be
moveable. The rectum opens to the outside of the pig, or the anus. The large intestine reabsorbs water from the digested
food, any undigested food is stored in the rectum as feces.
12. Lying on either side of the spine are two bean shaped organs: the kidneys. The kidneys are responsible for removing
harmful substances from the blood, these substances are excreted as urine. (more on this later)
13. Two umbilical vessels can be seen in the umbilical cord, and the flattened urinary bladder lies between them.
Checkpoint STAMP
Urinary and Reproductive Systems
1. Locate the kidneys; the tubes leading from the kidneys that carry urine are the ureters. The
ureters carry urine to the urinary bladder - located between the umbilical vessels.
2. Lift the bladder to locate the urethra, the tube that carries urine out of the body.
3. Note the vessels that attach to the kidney – these are the renal vessels
Male
1. Find the scrotal sacs at the posterior end of the pig (between the legs), testis are located in
each sac. Open the scrotal sac to locate the testis.
2. On each teste, find the coiled epididymis. Sperm cells produces in the teste pass through the
epididymis and into a tube called the vas deferens (in humans, a vasectomy involves cutting
this tube).
3. The penis can be located by cutting away the skin on the flap near the umbilical cord. This
tube-like structure eventually exits out the urogenital opening, also known as the urethra.
Female
4. In the female pig, locate two bean shaped ovaries located just posterior to the kidneys and
connected to the curly oviducts.
5. Trace the oviducts toward the posterior to find that they merge at the uterus. Trace the
uterus to the vagina. The vagina will actually will appear as a continuation of the uterus.
Checkpoint STAMP
PART III--Label
My favorite part of the dissection was___________________________________________
________________________________________________________________________
________________________________________________________________________